The overall objective of this project is to study in detail human Aumor-specific immunity directed against melanomass sarcomas and carcinomas, to correlate this with the clinical status of the patient's disease, and to define cellular variations in the expression of tumor- specific antigens. During the year 1974-1975 the following will be investigated: l. The serologic reactivity of patients with melanoma will be further defined by fluorescent antibody methods. More sera will Re titered and reactivity against fetal antigens will be investigated.2. Cell mediated reactivity to melanoma and bronchogenic carcinoma will be further studied and attempts will be made to define the effects of methodological variables, target cell specificity and the possibility that a common tumor-specific antigen is being detected by the 99mTc microcytotoxicity assay. 3. Attempts will be made to define the role of lymphotoxin in lymphocyte mediated target cell destruction. Cytotoxicity will be assessed in the presence and absence of rabbit antibody specific for human lymphotoxin. 4. The 99mTc microcytotoxicity assay will be further evaluated as a means of detecting tumor specific immunity in murine model systems with model systems with Moloney Sarcoma Virus (MSV) and methylcholanthrene (MCA) induced tumors. 5. Attempts will be made to determine whether blocking factors can be detected in the sera of tumor bearing patients and animals by means of inhibition of the 99mTc micro mixed hemadsorption reaction.6. Attempts will be made to determine whether immune complexes specifically or non-specifically inhibit cell-mediated immunity in vitro.